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authorDavid Vrabel <david.vrabel@citrix.com>2011-09-13 10:17:32 -0400
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2011-09-13 10:17:32 -0400
commite3b73c4a25e9a5705b4ef28b91676caf01f9bc9f (patch)
tree969df8ce6993364d0fcddffcd1a96e5dfa5a4c86
parentf10cd522c5fbfec9ae3cc01967868c9c2401ed23 (diff)
xen/e820: if there is no dom0_mem=, don't tweak extra_pages.
The patch "xen: use maximum reservation to limit amount of usable RAM" (d312ae878b6aed3912e1acaaf5d0b2a9d08a4f11) breaks machines that do not use 'dom0_mem=' argument with: reserve RAM buffer: 000000133f2e2000 - 000000133fffffff (XEN) mm.c:4976:d0 Global bit is set to kernel page fffff8117e (XEN) domain_crash_sync called from entry.S (XEN) Domain 0 (vcpu#0) crashed on cpu#0: ... The reason being that the last E820 entry is created using the 'extra_pages' (which is based on how many pages have been freed). The mentioned git commit sets the initial value of 'extra_pages' using a hypercall which returns the number of pages (if dom0_mem has been used) or -1 otherwise. If the later we return with MAX_DOMAIN_PAGES as basis for calculation: return min(max_pages, MAX_DOMAIN_PAGES); and use it: extra_limit = xen_get_max_pages(); if (extra_limit >= max_pfn) extra_pages = extra_limit - max_pfn; else extra_pages = 0; which means we end up with extra_pages = 128GB in PFNs (33554432) - 8GB in PFNs (2097152, on this specific box, can be larger or smaller), and then we add that value to the E820 making it: Xen: 00000000ff000000 - 0000000100000000 (reserved) Xen: 0000000100000000 - 000000133f2e2000 (usable) which is clearly wrong. It should look as so: Xen: 00000000ff000000 - 0000000100000000 (reserved) Xen: 0000000100000000 - 000000027fbda000 (usable) Naturally this problem does not present itself if dom0_mem=max:X is used. CC: stable@kernel.org Signed-off-by: David Vrabel <david.vrabel@citrix.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
-rw-r--r--arch/x86/xen/setup.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index ff3dfa176814..09688eb4a899 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -305,10 +305,12 @@ char * __init xen_memory_setup(void)
sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
extra_limit = xen_get_max_pages();
- if (extra_limit >= max_pfn)
- extra_pages = extra_limit - max_pfn;
- else
- extra_pages = 0;
+ if (max_pfn + extra_pages > extra_limit) {
+ if (extra_limit > max_pfn)
+ extra_pages = extra_limit - max_pfn;
+ else
+ extra_pages = 0;
+ }
extra_pages += xen_return_unused_memory(xen_start_info->nr_pages, &e820);

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